This invention relates to a mechanical linkage. More particularly, this invention relates to a system and method for estimating the position of a mechanical linkage.
Work machines, such as, for example, excavators and backhoes, often have one or more mechanical linkages that may be used for any number of purposes. For example, a wheeled excavator may include a digging linkage that extends from the housing of the excavator and one or more stabilizing arm linkages that extend from opposite sides of the excavator. The stabilizing arms are adapted to be raised and lowered to engage the ground and provide support and stabilization for the excavator when operating the digging linkage. A digging linkage, on the other hand, is typically configured for additional degrees of freedom. For example, the digging linkage may be raised, lowered, rotated, and/or pivoted with respect to the excavator to provide a full range of digging motion. Occasionally, an operator will operate the digging linkage in close proximity to the stabilizing arms.
Because controlling the operation of the digging linkage of a work machine is complex, inexperienced operators may risk bringing a portion of the digging linkage into undesired contact with other components of the work machine, including the stabilizing arms and the work machine body. This undesired contact may cause damage to the work machine. This damage may be expensive to repair and may reduce the productivity of the work machine and the workers at the work site.
To reduce the chance of interference between linkages, it is desirable to know the position of the various mechanical linkages. Some work machines use complex electrical equipment, such as displacement transducers, to determine the position of the linkages. However, work machines, such as excavators, are often used in environments that are harsh on this type of electrical equipment. Transducers that are manufactured to perform well in such harsh environments are expensive. Accordingly, although it may be economically feasible to place such transducers on frequently used linkages, such as the digging linkage, it may not be equally economically feasible to place displacement transducers on less used mechanical linkages, such as the stabilizing arms. Thus, while the actual position of the digging linkage may be easy to determine, the actual position of the stabilizing arms may not be known, thereby making it difficult to prevent undesirable contact between the digging linkage and the stabilizing arms.
One method for avoiding undesired contact between the digging linkage and the stabilizing arms is to restrict the range of motion of the digging linkage so that it cannot intrude into the entire region in which the stabilizing arms function. One system for restricting the range of motion of a digging linkage is disclosed in U.S. Pat. No. 6,131,061 to Denbraber. Denbraber relates to an apparatus and method for preventing xe2x80x9cunder-diggingxe2x80x9d of a work machine. The system defines an under-digging boundary relative to the work machine and prevents the digging linkage from moving past the under-digging boundary. This prevents removal of material that may cause the ground on which the work machine rests to become unstable. The system monitors the position of the digging linkage and restricts movement of the digging linkage to prevent under-digging the work machine.
Although such an approach eliminates the chance of contact between the digging linkage and the stabilizing arms, this approach may unnecessarily restrict the motion of the digging linkage. In particular, this approach may prevent the digging linkage from moving into certain regions about the work machine, even when the digging linkage would not contact the stabilizing arms. It is desirable to estimate the position of linkages on the work machine, such as the stabilizing arms, without the use of transducers, to allow the greatest range of motion of the digging linkage, while still preventing the digging linkage from contacting the other linkages.
The system of the present invention is directed to overcoming one or more of the problems or disadvantages set forth above.
In one aspect, the present disclosure is directed to a method of estimating the position of a mechanical linkage. An estimated position of a mechanical linkage is set to an initial position. A movement of the mechanical linkage is controlled based on a signal from an input device. The estimated position of the mechanical linkage is updated based upon the movement of the mechanical linkage. A determination is made when the estimated position of the mechanical linkage substantially corresponds to an actual position of the mechanical linkage.
In another aspect, the present disclosure is directed to a method of estimating a position of a first linkage to avoid interference with a second linkage. A range of motion of the second linkage is limited to a preset range of motion. A movement of the first linkage is controlled based on signals from an input device. A position of the first linkage is estimated based upon the movement of the first linkage. The range of motion of the second linkage is expanded based upon the estimated position of the first linkage.